1. Field of the Invention
The invention relates to a photonic label switching architecture, using an optical code correlation technique to replace photonic labels in the optical packet and handle the fully photonic label switching through the features of auto-correlation and cross-correlation, thereby omitting the photoelectric conversion for a photonic label.
2. Description of Related Art
The demand for enormous transmission capacity through optical fiber has been met so far by the wide scale deployment of wavelength division multiplexing (WDM). A direct mapping of Internet protocol (IP) onto the optical layer will eventually simplify the protocol architecture, to minimize the transfer delay in the core network. Further, to manage and access this bandwidth, the next growing challenge will most likely emerge at the switching nodes. The eventual goal is to reduce the amount of complex electronic components, and the cost, by migrating to the all-optical network, where data is switched and routed transparently in optical form. An optical packet switched network can provide high performance and fast switching with fine granularity for future networks. Photonic packet header processing for routing and switching will be needed to increase throughput and reduce latency. However, the processing capability of electronic routers will eventually result in bottlenecks in the foreseeable future, due to the explosion of IP traffic. Accordingly, one promising way to alleviate the capacity limit of the routers is to introduce a Multi-Protocol Label Switching (MPLS) technology.
FIG. 1 is a schematic diagram of a typical MPLS network. In FIG. 1, the network is formed by label switching router (LSR), e.g. LSR1-LSR5 where LSR1 is an ingress LSR and LSR5 is an egress LSR. As shown in FIG. 1, the solid line indicates a path between LSRs and its routing protocol and label distribution protocol, and the dotted line indicates label switching traffic flow. The principle function of MPLS is to utilize a label swapping forwarding algorithm to achieve the high-speed packet forwarding capability. It provides a label-steam which means mapping IP address to simple, fixed-length labels used by different packet forwarding and packet-switching technologies. Header processing and forwarding of IP packets are necessary at every router. This label can be used to save significant processing time by avoiding network layer label analysis at each hop and soaring processing demands at each network node. Moreover, the high-speed switching of data is possible because the fixed-length label is inserted at the beginning of the packet and can be processed by hardware through LSR1 and LSR53. Thus, switching packets can be very quick between links. MPLS routers use this kind of simple label-swapping algorithm replacing the standard destination-based hop-by-hop forwarding paradigm to quickly forward packets and enable scaling to terabit rates easily. Therefore, MPLS network can be well suited to the photonic-based network in which high-speed transmission is required. Here, it is referred to as photonic MPLS. A recent photonic MPLS is mainly devoted to wavelength MPLS network where the WDM technology is applied. When the logical topology of the wavelength MPLS network is established, the label switching paths (wavelength paths or light paths) are configured over the WDM physical network in order to carry IP packets utilizing the wavelength path. Here, the physical network describes an actual network which is similar to the network showed in FIG. 1. But the nodes are optical nodes and links connecting nodes are optical links. The LSRs in FIG. 1 are generally able to perform various operations on packet labels. However, it has been difficult to realize those functions in optical domain, i.e. for example, the wavelength MPLS network. Only one exception is label swapping changing the incoming wavelength to the different wavelength at the optical cross-connect switch. However, a high-speed wavelength conversion is difficult to perform on a packet-by-packet basis by the current technology. Therefore, functionalities of the core LSR are very limited in the wavelength MPLS network. To solve this problem, the light paths have to be set up in a circuit-switched fashion between ingress/egress LSRs. However, the bandwidth utilization of light paths will thus become very inefficient due to the photoelectric conversion delay. Additionally, the packet switching speed is limited by the photoelectric conversion, because the photonic header of a packet switching configured by the WDM technology has to be processed in electrical domain.